There is a marked difference between driver and passenger temperature even when set to unified. Air cold on driver probably 10-15 degrees warmer on passenger. Thermostat for passenger or mixing controller/actuator?

 

Make sure your coolant is not low. If it's good check the temp of the 2 hoses coming from the heater core. If the inlet is much hotter than the outlet then you might need to have the core flushed. Lastly you might have a blend door actuator in the HVAC malfunctioning.

 

Hi Fred,

I have a 2006 UL which had the same problem as you last year. I took it to a local auto A/C shop and he ran a colored dye test which showed my A/C lines were leaking badly. The lines are made of aluminum and corrode over time. Unfortunately for me, the shop didn't want to touch my car because replacing the lines requires separation of the body and frame.
The UL in particular has rear A/C lines connecting with the front, which made the job especially more difficult. Which is why people say on these forums avoid the UL if you want to lower your maintenance costs.

My local dealership also confirmed leakage. They were nice enough to offer me an option of cutting off the rear A/C and replacing only the front lines, saving money. But in the end I had them replace all the lines and install a new compressor which they said was also dead. Two weeks and $3,400 later, my car is ice cold. At least I had a free loaner (brand new NX 200t) during the whole wait time.

Along with checking your coolent, take my advice and have a local shop run a leak test. The test only cost me $50.
Good luck.

Joe

 

Can you put a thermometer in the driver and passenger side vents and post the temperatures?